When something good (an opportunity) is missed, most likely due to the persons rather apparent noobness.

Zie: I had a penis, she had a vagina, bloody missed opportunity.

Ebo: She had an orifice that would've fit perfectly around my penis, yet I only realised it after she dumped me.
Mike: Wow... missed opportunity buddy, maybe next time you'll notice that your girlfriends nostrils are perfect for your meat faster.

Nikki: "I entered a definition for 'missed opportunity' on Urban Dictionary, and all i could think of was definitions relating to sex. I had all these good ideas later on but, if only I had waited, damn irony."
Tanly: "That's isn't irony, foo."